This invention relates to prosthetic devices. In particular, the invention relates to a suspension system and method for a prosthetic device.
The suspension system for a prosthetic device serves to attach the device to the user's body. Commonly, a prosthetic device is attached to the remains of an extremity (e.g., a residual limb). It is necessary for the suspension system to ensure a comfortable fit of the prosthesis. It must also allow for the prosthesis to be easily and accurately controlled by the user and must ensure that forces exerted on the prosthesis are properly transmitted to the user's body via the residual limb.
A common complication of prosthetic device use is a reduction in volume of the residual limb during use of the prosthesis. This is due in part to pressure from the prosthetic socket on the limb, compressing tissue. Other medical factors including the user's internal fluid volume status may also have an effect. Loss of residual limb volume can lead to loosening, improper distribution of weight bearing forces and poor fit of the limb in the socket. This can cause increases in pressure and shear force on the limb, potentially leading to skin breakdown. It also results in a reduction of control over the prosthesis.
The current state of the art in prosthetic fabrication calls for the custom fabrication of a rigid socket which can contain the residual limb. The residual limb is covered with a liner made of elastomeric gel, polymer foam, fabric or other material. The socket is designed to have intimate contact with the liner-clad limb. A goal of the suspension system is to allow for good control of the prosthesis, and to resist the effects of changes in limb volume.
Methods of prosthetic suspension have been developed to address the problems of prosthetic control and control of limb volume changes. Historically, fabrication techniques did not allow for precise fabrication of a socket providing intimate contact. Much of the suspension was provided by straps, suspension sleeves or the passive suction created by placing the limb into the socket. This resulted in a looser fitting socket which reduced prosthetic control. Limb volume changes were addressed with donning or doffing of additional liners to make up for changes in volume.
Improvements in prosthetic design and fabrication now allow for more precise fabrication of the socket providing for intimate fit. Suspension is achieved with the use of a silicone liner with a locking pin, a suction socket with passive vacuum, and/or the use of a vacuum pump to create a vacuum within the socket, referred to as Vacuum Assisted Suspension or (VAS).
The background art is characterized by U.S. Pat. Nos. 4,075,589; 4,743,264; 4,781,720; 5,507,835; 6,002,317; 6,063,125; 6,229,422; 6,273,918; 6,387,096; 6,605,118; 6,797,008; 7,033,400; 7,144,429; 7,291,182; 7,817,004; 7,850,740; 7,914,586; 7,922,773; and 7,947,085; and U.S. Patent Application Nos. 2004/0143345; 2006/0293762; 2007/0191965; 2008/0243266; and 2010/0289359; the disclosures of which patents and published patent applications are incorporated by reference as if fully set forth herein.